Many materials and structures have been utilized to absorb energy during an impact. They range from fabrics and foams to plastics. Despite these materials and structures, there continues to be a need for structures with improved energy absorbing characteristics that are cost efficient to manufacture.
Recent materials include a sheet of material with a plurality of conical protrusions emanating from one side of the sheet. For example, U.S. Pat. No. 6,247,745 shows a base with a plurality of protrusions defined on the base where the walls of the protrusions at least partially compress during energy absorption. While suitable in many applications, a cost saving in manufacture of these structures might be available if the number of steps to manufacture these materials could be reduced. In particular, these prior art products require a production process that includes formation of the base and then formation of the protrusions within the base. Furthermore, the manufacturing methods used to make known materials result in inconsistent energy absorbers. For example, the walls of a protrusion may vary in thickness depending on the location of the wall that is measured. Furthermore, the thickness of the walls of one protrusion may vary from the thickness of the walls of an adjacent protrusion. Such unevenness leads to an energy absorber that is inconsistent in its ability to absorb an impact's energy. This causes uncertainty in the effectiveness of the energy absorber.
As weight of materials is always a concern in vehicle manufacturing, there continues to be a need for lightweight structures that have comparable or improved ability, relative to existing structures, to absorb energy while also being cost-effective to consistently manufacture.